A Coupled Tensor–DEM–FEM Model for the Whole Process of Internal Fine-Scale Damage to Surface Damage in Red-Bed Soft Rocks in the Coastal Area of South China

Round 1

Reviewer 1 Report

The manuscript «A coupled tensor–DEM–FEM model for the whole process of internal fine-scale damage to surface damage in red-bed soft rocks in the coastal area of South China» by Chang Xia, Yongtao Wu, Guangjun Cui, Jin Liao, Zhen Liu and Cuiying Zhou was submitted for peer review.

 

I read the submitted manuscript with great interest. The authors turned to a very urgent problem: study of characteristics of soft rocks of the coastal area of South China. The authors used the discrete element method combined with the finite element method. The Discrete Element Method (DEM) is a popular technique for analysis of the mechanics of granular matter, as well as for modeling multifracture situations in frictional materials such as concrete and geomaterials. The Finite Element Method (FEM), on the other hand, is a standard numerical technique for linear and nonlinear analysis of structures. Differently from the DEM, the FEM has difficulties for reproducing multifracture situations in solids. The combination of FEM and DEM procedures seems therefore a win-win situation for modeling and simulation of a wider range of problems in nonlinear mechanics, than using any of the two methods separately.

This approach is not new, and it follows that overall, the manuscripts does not provide anything relevant to the current scientific knowledge. At the same time, I would like to note that the manuscript addresses an interesting topic that has potential for application in mining.

 

Despite of the actual topic and well-conducted study, the authors have failed to prove the relevance of the study. The manuscript has significant flaws that need to be corrected. Correction of the shortcomings listed below must be done to improve the quality of the manuscript, enhance the ease of perception of the presented material and increase the interest of a readers.

 

1.) From my point of view, this number of keywords is very few. In addition, keywords should be more direct and related to the content of the manuscript. Keywords enable the reader to quickly search for the necessary material and enable the author to popularize their research and increase interest and citations. But if this number of keywords satisfies the requirement of the journal, this comment is advisory.

2.) The abstract is not quite formed correctly. It is very blurry and framed incorrectly. It seems that the authors have taken certain phrases from the text and thus formed the abstract. The abstract should clearly indicate the purpose of the study, its importance for society (i.e. to characterize the problem), identify the methods and materials of the study, and the conclusions should be clearly and briefly formulated. There is no "starting point" in the abstract, that is, information about previous studies (one sentence is enough). From my point of view, in the abstract, such information begins with the statement: "Previously conducted studies have established that ...".

2.1) It is desirable to avoid narrative text in the abstract.

2.2) Try to use words and phrases: an analysis has been carried out; studied; developed; proposed; established and so on. It is advisable to start sentences in the abstract with these words and phrases.

2.3) At the end of the abstract, it is necessary to indicate the result obtained by the authors, for example: A model has been developed that allows ...; A dependence has been established which is...; A pattern has been revealed...; An efficient system (technology) has been proposed, and so on.

The abstract should be revised.

3.) The manuscript has a sufficient list of references (36 references in total). But there is no full coverage of research in terms of geography of citations. There are not enough references to international studies in the field. The authors analyze the works of scientists of only one school. There are only 7 references to world experience. Almost all studies are older than 7 years.

The list of references is intended to demonstrate the depth of the authors’ study of the material, the relevance and interest of their research. 

3.1.) Depth of study is demonstrated with the number of references - is sufficient.

3.2.) Relevance – with the availability of research in recent years – is sufficient.

3.3.) Interest – with the availability of research by scientists from different countries - is not sufficient.

I ask the authors to take this recommendation seriously. Since you are publishing your manuscript in an international publication, it is necessary to demonstrate the international relevance and interest of this issue. This can be done by analyzing the studies of scientists from different countries. It is imperative to supplement the list of references with studies of scientists from different countries over the past 3-5 years to show geographical (general/global) interest and relevance.

Major revision of References might be sufficient if these tests have been performed. Otherwise, the paper should be considered as rejected in the present form.

Below I present a few papers relevant to this study that could greatly improve the manuscript. The authors have the right to use the material proposed or offer their own versions of international studies to increase the geography of citation.

4.) In the introduction when analyzing previous studies, the authors make inaccuracies or provide information that overloads the text and often their claims are not accompanied with evidence. It is important for readers to know the essence (main idea) of the research you are referring to when analyzing previous work. 

In the introduction, it is necessary to analyze the previously completed work and note what has been done, what are the shortcomings, and what has been done incorrectly. 

4.1) I am not a native speaker, but nevertheless, in my opining, the authors form a very long sentences, which are very difficult to perceive. Such sentences greatly reduce the easy perception of the material.

4.2) In the introduction, the authors refer to several works and quite rightly state what is done in this study. However, the authors do not explain why this study is interesting: what has been done right or wrong, what can be learned from the study, what needs to be corrected or improved and why this research is important.

4.3) «Tensor–DEM–FEM model» is claimed. However, authors did not reveal the background of «tensor–DEM–FEM model» issue: earlier studies, advantages and disadvantages of using the models separately, usefulness from earlier studies for this manuscript.

5.) I would recommend avoiding group references, for example [13-16], [18-22]. From my point of view, allowed up to three; more than three references are not acceptable and must be deciphered. Each paper you refer is unique and the studies you refer deserve more proper and careful review to demonstrate (and prove) its importance for the current research. It is necessary to demonstrate in detail the essence of each study and their need for your work. It has already been noted in recommendation (4.2) that you have many statements without indicating awareness. You will avoid group references by correcting this fact. Such flaws are present throughout the introduction. The authors need to revise the introduction, make adjustments, and supplement their statements with evidence.

6.) It is necessary to indicate who made figures 3, 4, 6? If this is the author's merit, then it is necessary to indicate: done by the authors; if this is a borrowed figures then please indicate the source.

7.) At the end of the introduction, there is no brief conclusion of the analytical study of earlier papers. The authors did not summarize their analysis and did not identify unresolved issues. This conclusion should make it possible to characterize the actual question posed, the purpose of the study and the tasks to be solved to achieve this goal. For example: Analyzing the above, it can be noted that ... is a very topical issue. Therefore, the purpose of this study is ... and to achieve this, it is necessary to solve the following tasks: 1); 2); ... Such a conclusion allows the reader to understand the vector of the study, and the authors to correctly formulate the conclusions. It needs to be improved. 

8.) Considering the comments (3), (4) and (5) I would like to note that the authors have very poorly disclosed the main subject of the study. Many works are devoted to the issues of safe underground operations in coal mines and metal mines. Researchers are faced with the task of improving safety and reducing accidents. For example,

8.1) Khayrutdinov M.M., Kongar-Syuryun Ch.B., Khayrutdinov A.M., Tyulyaeva Yu.S. Improving safety when extracting water-soluble ores by optimizing the parameters of the backfill mass. Bezopasnost' Truda v Promyshlennosti 2021, 2021(1), 53-59. https://doi.org/10.24000/0409-2961-2021-1-53-59.

The results of the scientific and research work devoted to modeling the stress-strain state of the mining system of an underground mine using the finite element method in the FLAC3D software are presented in the article. The results are presented concerning the research results of the quantitative assessment of the mass using the von Mises equation and Norton’ power law of creep to estimate the contour stress. It becomes possible to determine the sequence of mining of the deposit area and the stage-by-stage filling of the stopes at the stage of mining design due to the high accuracy of modeling the stress- strain state of the mass near mining operations using FLAC3D software. A differentiated approach to assessing the state of the mass is possible considering difficult mining and geological conditions, conditions of increased rock pressure, abundant water influx, increased fracturing of rocks by introducing additional conditions into the model depending on its geotechnical state.

8.2) Adigamov, A.E.; Yudenkov, A.V. Stress-strain behavior model of disturbed rock mass with regard to anisotropy and discontinuities. Mining Informational and Analytical Bulletin 2021, 8, 93–103. https://doi.org/10.25018/0236_1493_2021_8_0_93.

In this paper, a mathematical model has been developed to calculate the stress-strain state of disturbed rock mass, which considers the anisotropic properties of the environment. The proposed form of stochastic complex potential allows considering the radius of disturbance influence. The paper gives the solution of the main problem of the elasticity theory for an anisotropic environment weakened by several holes and the influence of these holes on each other.

8.3) Rybak, J.M.; Kongar-Syuryun, C.; Tyulyaeva, Y.; Khayrutdinov, A.M.; Akinshin, I. Geomechanical substantiation of parameters of technology for mining salt deposits with a backfill. Mining Science 2021, 28, 19-32. https://doi.org/10.37190/msc212802. 

This paper analyses the impact of underground mining on the undermined mass and suggests ways to minimize it. This impact is investigated using modelling in FLAC 3D. The order of disturbance development (from bottom to top), as well as the depth of critical disturbance development is established. Ways to minimize the impact of underground mining on the undermined mass are proposed. From my point of view, this study would be suitable to specify the statements and allow to expand the geography of citations.

8.4) Kongar-Syuryun, Ch.; Ubysz, A.; Faradzhov, V. Models and algorithms of choice of development technology of deposits when selecting the composition of the backfilling mixture. IOP Conf. Series: Earth Environ. Sci. 2021, 684(1), 012008. https://doi.org/10.1088/1755-1315/684/1/012008. 

In this study, the authors propose a methodology of selecting a mineral deposit development technology. The structure of the methodology includes fuzzy models and algorithms that provide processing of large amounts of information and form the significance of environmental factors. Each factor (criterion) is considered depending on its influence, that is, an influence coefficient or factor weight is introduced, which increases convergence.

If the authors become familiar with the works presented in (8.1), (8.2), (8.3), (8.4) they will be able to properly form the introduction, enrich their manuscript with international research by scientists from Azerbaijan, Poland, Czech Republic, Russia, Germany and demonstrate the depth of their material, as well as eliminate the remarks (3) and (4). This is very important for increasing citation geography and proving relevance.

9) The intersection of spheres when combining DEM and FEM methods needs to be clearly specified. Please note the following points:

9.1) What degree of hierarchy was used in combining the two methods?

9.2) What types of hierarchy were used?

9.3) When creating the hierarchical algorithm, were the weights of different types (criteria) considered? or assumed to be equal? If considered, how was the weight of each criterion determined? The determination of the weight of each criterion is described in study (8.4).

9.4) How is the DEM-FEM coupling procedure evaluated? (e.g. a simple example of particle-structure interaction can be presented).

9.5) Please provide a reference model or refer to the study where this model is borrowed from.

9.6) Specify boundary conditions, for example: particle radius, beam length, material properties (sphere radius, density, Young's modulus, Poisson's ratio, friction parameter), analysis parameters (initial velocity of the sphere, gravity, search for neighbors) and so on. I would recommend referring to (8.1) and (8.3) for a more accurate presentation of the modelling boundary conditions.

10) The proposed result seems to be well-founded and scientifically-based, but the lack of an application in a real-life situation is a noticeable deficiency in the manuscript. In this way, I believe the manuscript will gain a higher level of quality, which will allow the reader a greater possibility of evaluating the potential use of the result!

11.) From my point of view, there is no proof of the effectiveness and accuracy of the proposed research method. How to verify the effectiveness and accuracy of this method? Any case studies for this method?

12.) Conclusion is not correctly formed. Conclusion – summary of the study without repeating the wording given earlier in the manuscript. It is exactly the way of presenting the material that makes it easier for the reader to perceive the information presented. The mistake of incorrectly forming conclusion is a consequence of the incorrect presentation of the introduction noted by me in remark (7) due to the fact that when writing the introduction, the aims and objectives are not formulated.

The authors mention the object of the study in the conclusion, again referring to the methods, which is inappropriate for this section. The authors repeat throughout the manuscript. In my opinion, this information is unnecessary, as it has already been mentioned in the previous sections.

Conclusions should briefly characterize the result of the study, for example:

As a result of the study 

(1) the dependence of … was obtained.

(2) it was found that ...

(3) and so on.

The conclusion needs to be revised.

 

Summary: The manuscript is not a finished research work. The corrections are needed. The chosen research topic is relevant. From my point of view, the authors failed to present their research correctly and clearly, which reduced its value and worsened the ease of perception of the material presented. From my point of view, the manuscript cannot be published in the open press without correction in accordance with my suggestions. Major revision of manuscript might be sufficient.

Author Response

Thank you very much for your review of this article and your valuable comments. The author has modified the full text one by one according to your Suggestions. The specific modified content and the reply to the question are shown below.

Author Response File: Author Response.pdf

Reviewer 2 Report

·        Include the sampling locations map with some damaged pictures to highlight the field issue.

·        Instead of individual names in the research article, use proper citation. I personally don't know about the journal's instructions in this regard; however, I have neither practiced such methods in research articles nor seen them in my academic and research career.

·        Discuss the failure model selection in the process.

·        The modeling results are input parameter sensitive. How did the authors select/determine/calculate these parameters?

·        How about the idea behind Figure 4? Was it selected by the authors or based on existing literature? Please include a reference or discuss it comprehensively.

·        Figure 5: Avoid using basic terminologies via diagrams.

·        Ensure consistency in the citation of figures and tables in the body text and follow the journal's instructions (e.g., Figure, Fig). Also, make sure to cite the figure before it is presented (e.g., Figure 6).

·        What are the post-failure characteristics of the plot (Figure 8)?

·        Explain the differences between stage 2 and stage 3 in figure 8.

·        How can the study's findings be applied in the field?

·        Avoid including the methodology in the conclusion section. Base the conclusion on the study results.

·        Discuss the applications, limitations, and scope of the study.

minor corrections

Author Response

Thank you very much for your review of this article and your valuable comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Editors and Authors,

Thanks for this opportunity to review this manuscript. I appreciate the author's contribution to the field and believe that the paper is valuable and provides new insights into the subject matter.

The manuscript “A coupled tensor–DEM–FEM model for the whole process of internal fine-scale damage to surface damage in red-bed soft rocks in the coastal area of South China” can be improved to be suitable for publication. These are my comments:

1. In the abstract, the results obtained from the research should be presented briefly and as clearly as possible.

2. In this paper, a new concept is proposed for the study of the failure process in red-bed soft rocks using the coupled DEM-FEM model to explore the characteristics of the entire phase of its cracking - fracturing - breaking. The authors should describe exactly what type of rock it is, what the micro-scale structure is, what particularities these rocks present, and what the results obtained in the laboratory were (it is specified in line 128 that it is a low-intensity red mudstone). It is known that red mudstone is a dark sedimentary rock formed from consolidated mud and lacking the laminations of shale. These details are very useful for readers.

3. Figure 8 represents a schematization of the stages through which a rock passes from the moment of loading until breakage.

Referring to Figure 8: "C-D Crack stable development stage"; this portion of the characteristic curve also includes the stage of unstable or uncontrolled crack propagation. Until the dilatancy threshold is reached, crack propagation is stable and controlled, and when the dilatancy threshold is exceeded, the state of stress approaches the breaking stress. In the paper it is correctly mentioned that stages 5-6 involve the accelerated development of cracks (lines 333-334)

4. Line 511: It will be renamed Table 2 (Main Mechanical Parameters in a Discrete Element 2D Model).

5. I don't know if the word "catastrophic" is correctly used in the context of this study. I think it should be replaced with failure, breakage, or total damage.

Yours faithfully,

Minor editing of English language required

Author Response

Thank you very much for your review of this article and your valuable comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript «A coupled tensor–DEM–FEM model for the whole process of internal fine-scale damage to surface damage in red-bed soft rocks in the coastal area of South China» by Chang Xia, Yongtao Wu, Guangjun Cui, Jin Liao, Zhen Liu and Cuiying Zhou was submitted for second review.

As can be seen from the submitted manuscript and the explanatory note to the review, the authors did a lot of work to make changes in accordance with the comments. The revised manuscript is a completed scientific study on a highly relevant topic: study of characteristics of soft rocks of the coastal area of South China. The revised version of the manuscript, in my opinion, fully satisfies the requirements of a scientific article and can be published in the open press.

Reviewer 3 Report

I received and have checked all author responses to my comments and suggestions.  In my opinion, the paper can be accepted for publication now.
Yours faithfully